插装式压力阀RE21050

LC; LFA1/68

Rexroth Hydraulics 2/68LC; LFA

Function, section, symbols

General

The 2-way cartridge valves for pressure control functions are pilot operated poppet or spool valves. The main component designed as a cartridge valve (1) is inserted in a cavity bore standardised to DIN ISO 7368 and is sealed by control cover (2).

The pilot valve (4) for either manual or electrical proportional pressure control is integrated into the control cover (2) or mounted onto the control cover as a pilot valve with interface connections to DIN 24340 (2).

By combining the cartridge valve with the control covers different pressure functions can be realised.

Pressure relief function

Control cover type LFA..DB...Cartridge valve type LC..DB...

The cartridge valve (1) for the pressure relief function (type LC . DB…)is a poppet valve without an area differential (no effective area at port B). The pressure acting at port A is fed via the pilot oil spply orifice (5) to the spring side (6) of the element. At pressures below the setting of pilot valve (4) the forces on spool (3) are balanced and the spool remains closed due to the spring force. On reaching the set pressure, spool (3) opens and limits the pressure at port A in line with the pressure-flow characteristics.

Pressure reducing function

a) Normally open:

Control cover type LFA..DB...Cartridge valve type LC..DR...

The cartridge valve for the pressure reducing function is a spool valve without an area differential (no effective area at port B).

The same types of cover are used as pilot valves as are used for the pressure relief functions (type LFA..D...).

The pressure acting at port A is fed to the spring side of the spool via the pilot oil supply orifice. Below the performance limit and pressure set at the pilot valve, the spool is pressure balanced and is held open by the spring force, so that oil is free to flow from port B to port A.On reaching the set pressure, the spool closes and reduces the pressure at port a in line with the pressure-flow characteristics.

Type LFA..DB...Type LC..DB...

e.g.

Type LFA..DB...

Type LC..DR40...

LC; LFA 3/68Rexroth Hydraulics

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Function, symbols

b) Normally closed:

Control cover type LFA..DR...Cartridge valve type LC..DB40D...

For the pressure reducing function with opening characteristics a pressure relief valve cartridge (type LC..DB40D...) and a control cover with a pressure reducing valve (type LFA..DR...) as the pilot valve are used. The pilot oil is fed from port A via the pilot supply orifice and the open pressure reducing pilot valve to side B.

The main spool opens and allows free flow from port A to port B.On reaching the set pressure, the spool closes and reduces the pressure at port B in line with the pressure-flow characteristics. Possible excess pressures occurring on the secondary side are led away to tank via the third port of the pilot valve. By fitting a directional valve, an addi-tional isolating function can also be attained (type LFA..DRW...).

Example 2: (circuit for the pressure dependent sequencing of a 2nd system)

With this circuit, oil is allowed to flow into system 2 when the pressure in system 1 has reached a pre-set value. The pilot oil supply is internal from port A of the main valve.

Typical circuits

Example 1: (Circuit for the pressure dependent unloading of the low pressure system)

In the circuit shown, the system is fed by a high pressure pump and a low pressure pump. The system pressure p S acts externally from the high pressure side via the pilot oil port X on the pilot valve which, on reaching the set pressure, switches the low pressure side to give zero pressure circulation. The check valve RV (not included within the scope of supply) prevents the high pressure system from flowing into the low pressure system which is now at zero pressure.

Pressure sequencing function

Control cover type LFA..DZ...Cartridge valve type LC..DB...

This function enables a pressure-dependent sequencing of a second system.

The required sequencing pressure is set by the pilot valve which is integrated into the control cover.

The pilot oil supply may be either external (pilot oil port X) or internal (from port A via pilot oil port X or Z2).

The spring chamber of the pilot control is drained at zero pressure via ports Y or Z1 to tank.

e.g.

Type LFA..DR...Type LC..DB40D...

e.g.

Type LFA..DZ...XY

Type LC..DB20D...

e.g.

Type LFA..DZ...Y

Type LC..DB20D...

When the pressure set at the pilot control spring is reached, the pilot valve switches and unloads the spring chamber of the main valve to tank. The main spools opens and makes the connection from port A to B possible.

In model LFA..DZW..., the required spool position may be selected by means of an electrically operated pilot valve (not included within the supply of control cover LFA..DZW...) in addition to the normal hydraulic control.